sensitive skin must be considered. Others will be allergic, especially to fragrances and sometimes to preservatives,
and testing should include Allergic Contact Dermatitis assays for this volunteer group (a number of
major skin moisturizing products are now fragrance-free).
Since these products are used in a repeatedly “leave-on” fashion, the possibility of skin irritation and
dermal sensitization must be tested. The work can be done if the marketer has an adequately equipped bioengineering
laboratory or by professionals in clinical testing firms. A common patch testing site is the outer
(often hair covered) areas of the forearm or sometimes the back. Standard testing protocols are available,
such as the Acute Skin Irritation Test, the Cumulative Skin Irritation Test and the Sensory Irritation Test.
Aside from these volunteer-based tests, subjects must evaluate the application vectors. They include initial
skin feel (tactile smoothness and product uniformity); intermediate skin feel (hopefully minimum tackiness
as water in the emulsion evaporates) and final skin feel. Since aerosol moisturizing products are packaged in
BOV dispensers, where the bag is 100% filled with product, the emulsion must never stratify into oil and
water phases, even after a year or more.
If any separation does occur, no amount of shaking will reconstitute the layers—even temporarily. To
avoid these potential problems, skin care formulas contain emulsion stabilizers, often typified by having
long chain structures. For example, xanthan gum (produced by bacterial action) consists of a cellulosic core
with trisaccharide side chains. Although water-soluble and approved for foods, the polymer also has emulsion
and thickening properties.
A typical skin moisturizer can be illustrated as:
TYPICAL AEROSOL SKIN MOISTURIZER FORMULA
71.20% De-ionized Water
20.00% Isopropyl Myristate (IPM)
4.00% Glycerine (99%)
1.20% Sorbitan Isostearate
0.50% Petrolatum (White)
0.10% Dimethicone (AS D-C 200 Fluid–100 cstks.
0.03% Cetyl Alcohol
0.20% Polyglyceryl-3 Isodistearate
0.25% Xanthan Gum
0.05% Lactic Acid
0.02% Cyclopenta siloxane
0.02% Ceraryl Alcohol
0.04% Myristoyl Sarcosine
0.33% Ammonium Acryloyl Dimethyltaurate / VP Polymer
0.10% Dihydroxypropyl Trimonium Chloride (100% Basis)
0.10% Propylene Glycol
0.02% Hydrolysed Jojoba Esters
0.16% Propyl Paraben (n.Propyl p-Hydroxybenzoate)
0.16% Methyl Paraben (Methyl p-Hydroxybenzoate)
0.35% Disodium EDTA
0.20% Diazolidine Urea
0.47% Palmitoyl Pemtapeptide-3
0.50% Fragrance (hypo-allergenic)
While this is an untested formula, perhaps requiring the tweaking of percentages for
optimum results, it contains all the types of ingredients currently popular in existing skin
moisturizing products. This includes humectants, emulsifiers, emulsion stabilizers, a thickener,
preservatives, a film-former, a chelating agent, skin fresheners, fragrance and a collagen
prototype skin de-wrinkling agent. Those with molecular weights of about 4,500 daltons or
less are generally able to penetrate the 10–20 micron thick stratum corneun (SC) and reach
the underlying and much thicker stratum granulosum (SG), for added efficacy. The result is
tactile smoothing and a plumping of the skin
Evaluation techniques
Dry skin is caused when dermal moisture evaporates faster than the rate at which it can be
replaced. A new equilibrium is then established where the skin moisture content is only a
fraction of the normal level. In turn, this leads to skin that is bumpy, flaky and itchy. It can be
34 Spray February 2019
Xerosis—better known as dry skin—ranges from an
occasional winter-driven rash to disfiguring, flaky
“sandpaper skin.”
Curél Itch Defense Instant Soothing Moisturizing Spray with Advanced Ceramide Complex restores skin’s ceramide
levels to help retain moisture and prevent symptoms of dry, itchy skin from returning. The formula rebalances the
four components of healthy skin: ceramide levels, pH levels, moisture level and cellular turnover.